The invention relates to a shaft power plant and also to a shaft power plant module for generating electricity by energy conversion of a discharge between a headwater and a tailwater. To this end, the invention discloses a much simpler inflow concept for hydropower plants on damming structures, wherein all the important hydro-engineering requirements with regard to hydraulics, silt accretions, bed-load discharge, high water capability and also the necessary ecological components are taken into account.
On account of necessary climate protection, the continually increasing prices in the energy sector and further environmental effects, there are for the first time serious political commitments to sustainable energy concepts in Germany and also around the world. As a result of the positive development in the expansion of renewable energies, the German Federal Ministry for the Environment (Bundesministerium für Umwelt—BMU), in its 2007 progress report on the Renewable Energy Act (Emeuerbare-Energien-Gesetz—EEG), set a new expansion target of at least 27% electricity provision from renewable sources by the year 2020 and at least 45% by the year 2030. However, the BMU report also criticized the fact that the expansion of hydropower had hitherto remained far behind expectations. Causes for the stagnation in the expansion of hydropower in Germany were both the lack of economic incentives and also the high ecological requirements involving protracted and expensive authorization procedures. In addition, there was and is the risk of having to accept an application rejection, since evaluations are frequently made with nature conservation predominant and without objective assessment.
The fact that the BMU desires a further increase at all in electricity generation by hydropower, which is criticized by environmental organizations, can probably also be due to the fact that this manner of producing electricity is back in high regard on account of many environmentally relevant properties—high energy returned on energy invested, external CO2 costs, constant availability, relatively favorable production costs—and this has also been rewarded since January 2009 with increased rates of remuneration.
In Germany, a further expansion of hydropower is regulated by the provisions in the BMU's Guideline for the remuneration of electricity from hydropower and also by the European Water Framework Directive, wherein improved prospects for authorization exist in principle only for locations having existing transverse structures and simultaneous ecological improvement.
In reinforced-bed fluvial topographies, the basic water level must be protected, and so a local gradient jump must be retained even from ecological and economic points of view—ramp structures are expensive, are hydraulically inefficient for high water discharge and have a poor CO2 balance. The poor CO2 balance of ramp structures results from the quarrying and truck transportation of very large quantities of hard rock. This provides essential preconditions for hydropower utilization. When an ability to pass through is provided at the same time, the provisions according to the EEG guideline of the BMU must also be met. The construction of relatively large or large plants in Germany continues to be restricted thereby or is made more difficult or prevented.
On account of the established boundary conditions (EEG remuneration, defined requirements), the interest in new hydropower plants has increased considerably, in spite of site conditions that are not ideal. However, practice has frequently shown that economic efficiency can scarcely be ensured with conventional power plant technology, in spite of better remuneration, in particular with a decreasing drop height, and it could even be possible for stagnation to occur again. However, if there is a desire to generate more electricity from hydropower, even with less favorable conditions, because of its convincing environmentally positive properties, new technical components having an ecological orientation are required for more efficient use.
The benefit of promoting new, practical developments in this sector is additionally enhanced because more efficient hydropower concepts can be installed around the world.
Small-scale hydropower provides particular advantages for emerging and developing nations because, for example, with small drop heights only simple structural requirements are set for the damming structure, no reservoir banks are necessary and only marginal changes have to be made to the watercourse. Since, as a rule, the generation of electricity from run-of-the-river hydropower plants is largely ensured at least with partial load and occurs in a highly predictable manner, an important demand for supply reliability can be fulfilled even in decentralized settlement structures in isolated operation.
The technology for generating electricity from hydropower is in principle fully developed for larger plants, as is clearly documented by the extremely high overall efficiency of up to 90%. Even in partial load operation, excellent conversion into electrical energy can take place in virtually all types of turbine.
On account of the demand for renewable sources of electricity, in the last few years, more intensive research has been carried out in the field of small-scale and very small-scale hydropower. In addition to increases in efficiency and technological improvements in water wheels, a number of new types of turbine have been developed, these new types of turbine taking account to some extent of the issues of downstream fish migration and the passage of fish. Particularly noteworthy are in this case the technologies of matrix turbines and hydropower screws. Both types have in the meantime achieved a certain market maturity.
In summary, it can be established that improved types of turbine have been developed in niche segments. However, for the sites of interest having the defined boundary conditions according to the BMU guideline, it is not the type of turbine that is decisive but the efficiency of the entire plant concept, in which the particular hydraulic-engineering conditions of fixed, usually silted-up weir systems should be taken into account. An essential demand consists additionally in the ability that is to be created to pass through upstream and downstream, wherein harm to fish caused by turbines should be avoided.
Hydropower utilization for the relevant sites in Germany usually takes place in the conventional form of a bay-type power plant having high structural outlay and to some extent considerable encroachment in the banks. If no increases in the water level are allowed to be carried out, extremely unfavorable preconditions occur for the incident flow of the power plant on account of the low flow depths, and these preconditions can be circumvented to a limited extent only by deepening the inflows, which is associated with technical, operational and also economic disadvantages.
Since a virtually vertical screen plane arranged at a low level is specified, even in the case of bed-load discharge, extensive deepening of the bed has to be carried out in order that minimum hydraulic requirements for the flow conditions can be ensured. For this purpose, upstream basins for bed-load deposition and flushing sluices for bed-load transmission should be arranged in the upper inward flow region. The inflow structure must be designed and dimensioned such that the natural, wide flow cross section is diverted with as little loss as possible into the compact bay cross section. Operational analyses that have been carried out show that in operational bay-type power plants approximately ⅔ of the costs have to be estimated for the structural proportion.
Disadvantages of previously known bay-type power plants in overview: extensive flow diversion, extensive encroachment in the banks, extensive deepening of the bed, which has to be protected by a bed-load sluice, noise pollution, to some extent negative visual effect on account of power plant buildings and ecological impairment of the previous stretch of river between inlet and outlet with downstream fish migration which is difficult to achieve.
It is the object of the invention to provide a hydropower plant which can be operated in an environmentally sound and efficient manner while being cost-effective to produce.
The object is achieved by the features of the independent claims. Advantageous developments are the subject matter of the dependent claims.
In order to be able to achieve increases in efficiency, a fundamental change in the plant design is necessary. The invention set out in the following text involves essentially a change from the vertical inflow plane to the horizontal inflow plane by means of a vertical shaft, from which considerable hydraulic, ecological and economic advantages can be derived. The invention involves an underwater hydropower concept, preferably at damming structures. In this case, damming structures should be understood as meaning in particular river barriers, dams, check dams, dam walls, weir systems, historic and also landmarked weir systems, transverse structures, locks, plants regulated by dams and/or the damming of flowing or standing waters. Furthermore, the expression damming structure relates here to a natural barrier between a headwater and a tailwater. All important hydraulic-engineering requirements with regard to hydraulics, silt accretions, bed-load discharge, high water capability and also the necessary ecological components are taken into account according to the invention.
Thus, the invention is achieved by a shaft power plant for generating electricity by energy conversion of a discharge between a headwater and a tailwater, comprising a vertical shaft, the top of which forms an inflow plane which is parallel to the bed and extends below the water level of the headwater, wherein the shaft is open toward the top and is closed by a base at its bottom end, a unit composed of a turbine and an electrical machine, wherein the unit is arranged entirely under water in the shaft and wherein the turbine is arranged for water to pass through vertically, and an outflow, which is connected to the turbine, represents a closed flow channel and leads through a through-passage in the shaft to the tailwater, wherein, in a horizontal plane of a turbine runner of the turbine, a first cross-sectional area of the shaft is much larger than a second cross-sectional area taken up by the turbine runner.
The first and the second cross-sectional area both extend horizontally in the same plane. The first cross-sectional area is measured with the unit composed of the turbine and electrical machine being disregarded. In other words, the first cross-sectional area is, for example in the case of a rectangular shaft, the product of the two clear side lengths of the shaft. The second cross-sectional area corresponds to a flow cross section in the turbine channel and is specified for example by the product of half the diameter of the turbine runner squared and pi. In a preferred configuration, it is provided that the first cross-sectional area is at least 1.5 times, in particular 5 times, in particular 10 times, in particular 30 times larger than the second cross-sectional area.
The definition “inflow plane which is parallel to the bed” also includes an inflow plane which is inclined slightly, in particular by +/−5°, with respect to the bed plane. The bed plane can deviate from the horizontal in particular in check dams.
The unit is characterized by a compact construction, preferably having a permanent magnet synchronous generator having a variable speed and/or a direct coupling between the turbine and the electrical machine and/or virtually maintenance-free underwater operation. As a result of these properties, there is no need for a power house building and only the electronics needs to be set up in a container or building away from the water. On account of the specific construction of the turbine which is flowed through vertically, a fundamental change in the inflow plane and screen plane can be carried out.
The shaft power plant according to the invention enables more cost-effective hydropower utilization on flowing waters having transverse structures in order to generate different energy levels in the body of water. Typical examples of such sites of application are, inter alia, existing transverse structures and historic weirs. The concept can also be applied at other sites, for example at check dams or in medium pressure systems which are silted-up or at risk of silting up, and also in artificial lakes and reservoirs.
The potential of such sites is also present in Germany and can be implemented economically on account of the optical advantages and low construction costs. As a result of the simple arrangement, the robustness and low maintenance requirement, the relatively low construction outlay and the possibility of working in a modular manner with prefabricated elements, use outside Germany and Europe, around the world, in particular also in developing nations, is possible.
With the concept of the shaft inflow, on account of the horizontal arrangement, the frequently required quotient of Qturbine/Ascreen area<0.5 m/s can be achieved much more easily and cost-effectively, because the shaft cross section has to be increased only two-dimensionally and furthermore no areas of the banks are taken up. Previously known bay-type power plants often achieve only Q/A=1 m/s. Q is the discharge in the turbine in m3/s. A denotes the shaft cross-sectional area in the screen plane. In order to protect fish, the shaft cross-sectional area in the screen plane has to be selected to be large enough for the fish to be able to perceive the barrier and to react and to be able to escape under their own power, and for their physical capabilities to escape not to be exceeded, in other words, in extreme cases, Qturbine/Ascreen area<0.3 m/s should be preferred.
It is further preferred for the shaft top, or inflow plane, to extend in the bottom half, in particular in the bottom third, of a water depth of the headwater.
Advantageously, the shaft is open over its entire top side, with the exception of any screens. It is also advantageous for all of the side walls of the shaft to extend vertically, so that the first cross-sectional area is constant over the entire shaft depth. As a result, any restriction in the incident flow is prevented and the shaft can be produced very simply. The expression “vertical” side walls also includes a slight inclination, in particular +/−5°, with respect to the shaft base. It is also preferred for the shaft to be configured with deflecting walls that extend in a flow-favorable manner.
In a preferred configuration, the turbine, in particular the turbine runner, is arranged below the bed plane of the headwater and/or is arranged in the bottom half, in particular in the bottom third, of the shaft. The turbine and the electrical machine are preferably arranged clearly below the shaft top. In high channel flows, bed-load can pass into the shaft, the bed-load is flushed over the shaft by the positioned flap, i.e. the height of the shaft with regard to the river bed and the position of the turbine wheel below the inflow edge that holds back the bed-load are important.
It is advantageous for a rotational axis of the turbine runner and an armature axis of the electrical machine to be arranged coaxially with one another and vertically. Furthermore, it is preferably provided that the outflow widens, in particular continuously, directly after the turbine. It is particularly preferred for the curved outflow to comprise, in the following order downstream of the turbine, a flaring cone, an elbow and a suction pipe or a suction hose.
The suction pipe or suction hose are configured preferably as a diffuser for recovering the velocity energy. The elbow serves preferably to divert the flow into the horizontal or virtually the horizontal. Preferably, the elbow diverts through 80° to 100°, in particular through 85° to 95°, in particular through 90°.
Preferably, the base of the shaft is arranged below the bed plane of the headwater. The shaft thus extends as far as below the bed plane of the headwater.
Preferably, the curved outflow, in particular configured as a pipeline, is arranged above the turbine runner, so that during electricity generation the water flows through the turbine runner from bottom to top. In this case, it is advantageous for the curved outflow to extend through a side wall of the shaft to the tailwater. By way of this arrangement, overall depth can be saved in the case of small drop heights, thereby entailing considerable cost advantages.
As an alternative, it is preferred for the, in particular curved, outflow to be arranged under the turbine runner, so that during electricity generation the water flows through the turbine runner from top to bottom. In this case, the curved outflow preferably extends through the base of the shaft to the tailwater. It is further advantageous here for the shaft to be configured to form a cavity underneath the base, wherein the base of the shaft forms a ceiling of the cavity and wherein the curved outflow extends through the ceiling, the cavity and a side wall of the cavity as far as the tailwater. The cavity is filled preferably with ballast in order to ensure safety against buoyancy.
In a further advantageous configuration, the inflow into the shaft is provided with a horizontal screen plane, which corresponds to the horizontal inflow plane, or a vertical screen plane having in particular a horizontal cover over the shaft. Preferably, use is made of an upstream coarse screen and a downstream fine screen. The fine screen is configured preferably with a grating spacing of <20 mm. Preferably, both screens have rotatable screen bars and/or a mechanical cover, e.g. a rolling cover, and also a screen cleaning device under water.
Preferably, the shaft power plant comprises a damming structure between the headwater and the tailwater. In this case, damming structures should be understood as meaning in particular river barriers, dams, check dams, dam walls, weir systems, historic and also landmarked weir systems, transverse structures, locks, plants regulated by dams and/or the damming of flowing or standing waters. Furthermore, the expression damming structure relates here to a natural barrier between a headwater and a tailwater.
Preferably, a flap which is permanently overflowed is arranged in the damming structure, in particular over the entire inflow width. Preferably, the shaft is configured with a polygonal or semicircular cross section, wherein one longitudinal side butts directly against the damming structure. Further preferably, the flap can be pivoted about a horizontal axis to enlarge the overflow and simultaneously to open an underflow. As an alternative to the pivotable flap, a rotary flap is preferred, wherein the rotary flap comprises on its bottom edge an integrated closure which allows the underflow to be regulated depending on the overflow.
The headwater level is regulated up to the maximum normal discharge of the turbine by the vane position of the preferred guide apparatus and the speed of the turbine runner. On account of the compact structural form with forced vertical diversion of the works water, a pronounced eddy formation is produced at the transition from free flow discharge to pressurized discharge. As was shown by the experiment on the physical model, even a relatively small, wide flap overflow prevents rotary flow with eddy formation that draws in air.
By way of the flap arranged on the end side, four essential effects are achieved:
Prevention of eddy formation in the inflow by permanent overflow with simultaneous oxygen regulation. In this case, it is possible to regulate both the introduction and the removal of oxygen in the case of oversaturation. Wide and direct surface outflow into the tailwater. Eels, which live close to the bottom and only swim downstream on a few days in the fall could be allowed to pass into the tailwater without being harmed by temporarily opening the integrated cleaning closure, which is flush with the bed, or, if a pivoting flap is installed, by rotating the latter. Removal of driftwood and floating debris via the flap and removal of the screening material under the flap. And also, if appropriate, control of the headwater level.
On account of the permanent overflow of the flap, laminar flow close to the surface develops in the entire inflow region, as a result of which fish which particularly wish to migrate, in particular young fish that live predominantly at the surface, can descend without being harmed.
In order to meet the preferred requirements, a rotary flap must be equipped with a low, integrated closure. The alternative pivoting flap has a centrally arranged pivot pin, as a result of which a rotational movement in the clockwise direction simultaneously ensures or increases the under- or overflow. In order to be able to open the entire surface cross section in high channel flows and not to cause the risk of a log jam, use is preferably made of technology which allows the central pivot pin to be uncoupled and a pin at the bottom of the flap to be inserted.
Preferably, a bottom edge of the flap is arranged at the level of the shaft top.
Alternatively, it is advantageous for a flushing channel, which is located lower than the shaft top and lower than the bed plane of the headwater, to extend around the shaft, wherein the flushing channel leads to the flap and the bottom edge of the flap is arranged at the level of the flushing channel. The flap is preferably provided with a regulating device which is suitable for producing a bed-load discharging flushing surge.
Bed-load discharge takes place in the case of larger channel flows, wherein complete silting up can occur very frequently up to the shaft top in fixed weir systems. On account of the relatively small coverage, the flap flushing system according to the invention is effective. In conventional plants, complicated and extensive flushing structures are required on account of the subterranean development. By way of fine screening, the introduction of coarse bed-load is prevented, sands cause virtually no damage to the turbine in the low-pressure range.
Bed-load discharge and driftwood transport usually take place in high channel flows. In order to avoid corresponding mechanical and structural damage, the screen bars can preferably be designed in a rotatable manner (use as closure plane) in order to prevent the introduction of bed-load and floating matter into the shaft. At the same time, in the case of higher channel flows, the flap closure is designed with the effect that a drawdown curve forms over the screen plane and sufficiently large entraining forces are generated thereby to keep the inflow region free of bed-load. The shaft and flap should be dimensioned for the required full-area flushing action.
In conventional inflows, fish migrating downstream can be pushed against the inflow screen at high flow rates or get into the turbines of hydropower plants, as a result of which they risk being harmed. With the technical corrective measures carried out hitherto, it was possible to achieve at best partial successes. Thus, bypass systems for downstream fish migration are often without effect and constructive turbine solutions (runner geometry, speed) are associated with considerable losses of efficiency, with the question of the actual reduction in harm remaining open. According to the invention, a considerable reduction in harm to the fish stock is possible on account of the creation of safe migration corridors into the tailwater and the lowering of the incident flow speeds in the screen plane to preferably vm<0.5 m/s. In order to meet just the requirements for low incident flow speeds, in conventional power plant inflows having a vertical plane, the structures would have to be considerably increased in size, since hitherto dimensioning was carried out with vm screen≦1.0 m/s.
With the concept of the shaft inflow according to the invention, on account of the horizontal arrangement, the required large screen surface can be produced with moderate flow rates without expensive ramp structures. The second requirement for functional migration corridors remains largely unmet in conventional power plants. With the shaft concept according to the invention, on account of the flap arrangement having the hydraulically necessary permanent overflow, there is the possibility, by preferably triangular or semicircular indentation in the top region of the flap, of reinforcing the direct outflow such that it is used by fish which wish to migrate. Eels, which live close to the bottom and only swim downstream on a few days in the fall, could be allowed to pass into the tailwater without being harmed by temporarily opening the integrated cleaning closure, which is flush with the bed, on the bottom edge of the flap. The proposed downstream fish migration techniques are promising because, in addition to the low flow rates in the fine screen plane, there is a short and direct path to the wide flap overflow or underflow. Preference is given to both continuous and (sensor) controlled operation, in which particular consideration could be given to the time periods for downstream fish migration.
On account of the preferred direct positioning of the shaft according to the invention at the weir body or damming structure, and also the fully underwater arrangement, further positive effects are achieved: completely invisible power plant buildings, retention of the waterway in the river bed without serious flow diversions and impairment of the ecological fauna and ecological flora, no formation of dead zones in the tailwater, and avoidance of noise pollution on account of the fully underwater arrangement.
Also preferred are adjustable screen bars as a closure device and/or other motorized covers and/or underwater screen cleaners and/or an integrated closure part, necessary for the transmission of the screening material, on the bottom edge of the flap.
Preferably, the upwardly directed outflow should be employed in low pressure plants, in order to save on the overall depth. Further preferably, the invention is also used in medium pressure plants, wherein in this case the shaft can be used to prevent the turbine inflow from silting up. The design of the screen, the arrangement of the screen and the flushing flaps play an important role in particular in low pressure plants.
As an alternative to the recessed arrangement of the shaft in the bed, it is preferably provided that the base of the shaft is arranged above the bed plane of the headwater. Preferably, to this end, the shaft is supported on the bed and/or fastened to the damming structure, in particular suspended, and/or arranged in a manner standing on a protrusion from the damming structure. Particularly preferably, the outflow comprises a cylindrical throughflow of constant cross section, in particular configured as a borehole, through the damming structure. The cylindrical section is adjoined preferably by a cross-sectional widening, in particular a diffuser, as the transition to the tailwater.
This variant is used preferably in medium pressure plants or in conventional dams. The shaft height on the damming structure is selected in a manner depending on the height of the dam and the silting scenario. The recovery of energy in the diffuser takes place preferably only on the air side.
As an alternative to the direct attachment of the shaft to the damming structure, the shaft is set up on the bank or bored directly into the rock or constructed in the rock. In this case, an existing diversion cut can be used in a modified manner as a connection to the tailwater. The shaft is configured preferably as a cylindrical borehole, in particular in the rock. In the case of stable rock, the walls of the borehole, that is to say the rock itself, forms the shaft wall directly. Alternatively, the shaft can be inserted into the borehole or be concreted in the borehole. Provision is furthermore advantageously made of an inward flow from the headwater into the shaft or into the borehole by means of a diversion. Two variants of a shaft in the rock are preferred. In the first variant, the lake contents (headwater) are turbined into the tailwater via a shaft in the rock. In the second variant, diversions are turbined into the lake. Diversions guide the water in the free flow discharge from a different valley into a pool. This means that there is always a difference in level between the arriving free flow discharge and the water level in the pool. This difference, which is reduced as the pool fills, can preferably be used energetically. In previously known methods, this difference is not used and the water runs over the rocks into the reservoir.
An overview of the advantages of the shaft power plant according to the invention: marginal flow diversion on account of the preferred modular construction and preferred multiple arrangement of a plurality of shaft power plants at a damming structure, turbines can be integrated in and on the weir without serious flow diversion, shaft inflow with a horizontal screen plane, little deepening of the bed by way of end-side flap flushing, no structural encroachments on the banks, no noise pollution, no generator cooling necessary, no visible power plant buildings, downstream fish migration possible via continuously charged flushing flap.
The invention furthermore comprises a shaft power plant module for generating electricity by energy conversion of a discharge between a headwater and a tailwater, comprising a vertical shaft module, the shaft top of which forms an inflow plane which is parallel to the bed and is configured to extend below the water level of the headwater, wherein the shaft module is open toward the top and is closed by a base at its bottom end, a unit module composed of a turbine and an electrical machine, wherein the unit module is configured to be arranged entirely under water in the shaft module and wherein the turbine is configured to be arranged for water to pass through vertically, and an outflow module, which is connected to the turbine, represents a closed flow channel and is configured to lead through a through-passage in the shaft module to the tailwater, wherein, in a horizontal plane of a turbine runner of the turbine, a first cross-sectional area of the shaft module is much larger than a second cross-sectional area taken up by the turbine runner.
The advantageous configurations, as have been discussed in connection with the shaft power plant according to the invention, are preferably applied in a corresponding manner to the shaft power plant module according to the invention. The separate shaft module, which can also be set up independently of a damming structure, comprises a shaft, which is flowed through vertically, and a turbine having an electrical machine, these being arranged permanently under water. The shaft module can be set up freely in a naturally or artificially dammed body of water or be built onto (hydraulic) structures having different functions. The shaft module integrates preferably a horizontal screen plane having a cleaning means. Eddies must be prevented by means of hydraulic measures. The modular construction allows the shaft power plant to be set up in a manner locally detached from (e.g. upstream of) a damming structure to be erected, an already existing dam or in an existing water pool. A hydraulic connection between the headwater and the tailwater must be ensured in each case.
The shaft power plant or shaft power plant module according to the invention comprises preferably a shaft having a simple cross section, in particular rectangular or circular or semicircular, having vertical or almost vertical walls. In any case, the usual flow-favorable constriction toward the turbine is preferably avoided and thus a cost-effective shaft geometry is selected. For flow diversion, simple guide elements or an optimized guide apparatus of the hydraulic machine can preferably be used. Guide elements formed in a flow-favorable manner, in particular guide elements that extend in a spiral shape are preferably arranged in the shaft. The cross section of the shaft is preferably much larger than that taken up by the turbine runner. In previously known equipment, the different cross sections are compensated by a complex, curved shell, in order to keep losses low. By contrast, in this case preferably a hydraulically unfavorable geometry is selected, with the unfavorable flow path being offset by a large cross-sectional area and possibly by guide elements and/or guide apparatus. The speeds are low on account of the large cross-sectional area and the hydraulic losses are correspondingly also low.
Preferably, in the proposed power plant, use is not made of an air space, a means of access or a lateral connection in the form of a conventional, accessible power plant control center. In previously known equipment, the turbines are set up in a dry, cohesive space, specifically alongside one another, i.e. one turbine per inflow. According to the invention, there is no such transverse connection.